This invention relates to a silver halide photosensitive material and a process for the production thereof. More particularly, it relates to a photosensitive material for room-light.
In recent years in the field of graphic arts an improvement of efficiency in the reproduction working process is requested to cope with the complexity of prints and the progress of a scanner. In order to comply with the request an extremely low-sensitivity photographic film having a sensitivity as low as about 10.sup.-3 to 10.sup.-5 times that of a conventionally used contact negative film has already been developed and begun to be used as a reproduction film capable of being treated under UV-free room-light, namely, as a photosensitive material for use under room-light. The performance characteristic required for such a photosensitive material for use in room-light include a high contrast with a sufficiently high maximum density, tolerance for a long-lasting treatment under room-light, and a high sensitivity to a printer light source. The conventional photosensitive materials for use under room-light, however, are hardly said to meet sufficiently the above requirements and there is a demand for the development of more improved photosensitive material for use under room-light.
The silver halide emulsion for photosensitive materials suitable for use under room-light may be produced by the method described in Japanese Patent Application "Kokai" (Laid-open) No. 125,734/81, which employs as an inorganic desensitizer a large amount of rhodium salt in a silver halide emulsion containing silver chloride as major component, or by the method which employs an organic desensitizer usually used in a direct-positive silver halide emulsion, such as Pinacryptol Yellow. The present inventors found, however, that the emulsion produced by either method has an essential disadvantage as a room-light photosensitive material in that it gives only an insufficient guarantee for the safe treatment under room-light. The emulsion containing a rhodium salt is subject to considerable fogging under room-light, while the emulsion containing an organic desensitizer suffers from considerable decline in sensitivity when an imagewise exposed emulsion is left standing under room-light even for a short period of time before development, though the emulsion is treatable under room-light without fogging for an extended period of time. Although it is, of course, possible in the latter case to avoid the decline in sensitivity by developing the emulsion immediately after the imagewise exposure, still the safety for the treatment under room-light is requested to be improved, because the emulsion is frequently left standing under room-light when a large number of photographic materials are successively exposed or for other reasons.